Chances are you’ve seen lighthouses and know that they illuminate the waterways along the coastal regions in many areas of the world. You may not have realized though that the lenses that are used in the lighthouses are typically of the Fresnel variety that were invented by a French physicist named Augustin Fresnel in 1822. The lenses have a beehive appearance and the light sits in the center.
The Fresnel lens, sometimes close to 15 feet high, are made designed of concentric rings of glass prisms both above and below; they bend the light into the narrow beam that illuminates the waterways and are powerful enough to cut through the heaviest fog. The beehive design helps to capture and reflect the light and focus the beams out onto the water to help safely guide marine vessels to shore or direct them away from dangerous areas.
Lighthouse in California
The lenses used in lighthouses are shaped like a magnifying glass as a way to make the concentrated beam even more powerful. When the lenses were first used, fire was the main source of illumination and inventors found that without reflectors being placed behind the flame, it lost nearly 97% of its illumination. The Fresnel lens, because of its unique design, captured all but 20% of its illumination and its magnifying efficiency meant its light beam could be seen more than 20 miles into the darkness.
Fresnel lenses were found more prevalently in Europe as lighthouse keepers readily accepted the new “technology.” It wasn’t until the late 1800s that lighthouses in the United States were converted because many of the US lighthouse keepers believed the lens was a fad.
UKA Optics is a manufacturer and designer of lenses for industrial, medical, high tech and electronic applications.